1. Field of the Invention
The present invention relates to an apparatus for and a method of controlling a variable valve timing mechanism that changes the closing timing of an intake valve of an internal combustion engine.
2. Description of Related Art
Japanese Laid-open Patent Publication No. 2010-138737 discloses a controller of a variable operating angle mechanism capable of changing an operating angle of an intake valve. The controller controls the operating angle of the intake valve before startup of the internal combustion engine, so that the closing timing of the intake valve becomes after piston bottom dead center. Then in a startup state from input of a command signal for starting up the internal combustion engine until combustion starts, if the temperature of the internal combustion engine is lower than a threshold, the operating angle of the intake valve is made smaller that before startup, so that the closing timing of the intake valve approaches piston bottom dead center.
In the control by the controller, completion timing of the control for causing the closing timing of the intake valve to approach piston bottom dead center is after rotation of a starter motor, in other words, after cranking rotation is stabilized.
Incidentally, in a state with the closing timing of the intake valve being largely retarded after piston bottom dead center, that is, in a decompressed state, the effective compression ratio is low, and pre-ignition can be suppressed and vibratory force can be decreased. However, if the effective compression ratio is low, the combustion torque of the internal combustion engine decreases, and hence, the rise in engine speed in the cranking state becomes slow, and cranking time increases.
Consequently, in the control by the controller in which completion timing of the control for causing the closing timing of the intake valve to approach piston bottom dead center is retarded, power consumption at the time of startup of the internal combustion engine is increased.